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Estera J. Igras, Matthew Ratzlaff, James Loughman, Colm O Brien; Macular Pigment Optical Density and Glaucoma. Invest. Ophthalmol. Vis. Sci. 2012;53(14):2217.
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Macular pigment (MP), expressed as macular pigment optical density (MPOD), plays an important role in visual function and is implicated in the protection of the retina from oxidative damage. It is not known whether glaucoma, a progressive neurodegenerative disease of the optic nerve, is associated with alterations in MP. We sought to assess whether MPOD is affected by glaucoma and if so, does it correlate to glaucoma severity as judged by the extent of subjects` visual field defects?
40 subjects with glaucoma were recruited from a glaucoma clinic and underwent a comprehensive eye examination including assessment of visual fields using SITA-fast. Caregivers and those attending with the subjects, with normal visual acuity and no history of eye disease, were recruited as normal controls (NC), (n=54). For subjects and NC, the eye chosen was selected randomly. MPOD, at 0.50 of retinal eccentricity, was determined using heterochromatic flicker photometry, measured using the Macular DensitometerTM. Visual field defects were recorded as both median deviation (MD) and pattern standard deviation (PSD). Glaucoma severity was classified using MD, into mild glaucoma (MD < -6 dB), or moderate to severe (any readings > -6dB). The data was tested for normality with the Shapiro-Wilk test. Most of the data was normally distributed and was analysed using student t- tests. Non normal data was analysed using a Mann-Whitney U test. The Pearson correlation coefficient was used to determine correlation between MPOD and the visual field scores.
The mean age +/- standard deviation (SD), of subjects with glaucoma was 69 +/- 11 years compared to 66 +/- 10 years for NC. Mean MPOD (SD) for patients with glaucoma was 0.275 (+/-0.25). Median MPOD (Interquartile range, IQR) was 0.36 (0.44) for NC. The difference in MPOD between the glaucoma cases and NC was significant, (z= -2.158, p =0.031). Mean MPOD for those classed as mild glaucoma was 0.325 (SD +/-0.27), n=12, compared to 0.254 (SD +/-0.24) for the moderate to severe group, n=28, although this difference was not statistically significant.(p =0.42). The Pearson correlation coefficient showed a non-significant, weak correlation between MPOD and both MD (r =-0.1, p=0.6) and PSD, (r=0.16, p=0.43).
These findings suggest that MP is reduced in patients with glaucoma. The severity of glaucoma, as judged by the MD of visual field scores, did not significantly affect MPOD. This is confirmed by a weak correlation between overall MPOD and the extent of visual field defects. The median MPOD for NC was consistent with levels published elsewhere. Further investigation is needed to determine the significance of MP change and to assess what role therapeutic strategies aimed at increasing MP levels could have in the management of glaucoma.
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